We have constructed and tested the immunogenicity of formaldehyde stabilized, envelope (Env) modified heat treated pseudovirions as vaccines for HIV. Interestingly, in preclinical studies, vaccination with a formaldehyde stabilized, a heat treated pseudovirion vaccine bearing deletion of a single N glycan residue in V1 in conjunction with a mutation in the endocytosis and cell sorting signal in gp41 demonstrated induction of high titer 50% neutralizing antibodies against heterologous primary viruses. Whereas immunization with this vaccine did not improve neutralizing antibody responses against homologous virus as compared with a vaccine bearing wild type Env, we observed between 1.8 and 10 fold increases in GMT when heterologous primary viruses were tested in these neutralization assays (individual titers ranged from 20-4,860 depending upon which viral isolate was tested and which assay was employed). We hypothesize that antibodies induced by vaccination with this immunogen recognize conserved epitopes on Envs of multiple clades, and that identification of those epitopes may yield important structural information that could be used to improve vaccines aimed at eliciting broad neutralizing antibody responses. We propose here to isolate and utilize monoclonal antibodies from immunization studies in diverse pre clinical model systems to characterize the neutralizing antibody response induced by this vaccine in order to further define correlates of antibody- mediated protection. These antibodies will be isolated using non traditional methods which we hypothesize will allow us to isolate more physiologically relevant antibodies than are obtained with traditional hybridomas technologies. As of December 2004, nearly 1 million people were living with HIV or AIDS in the United States, with 44,000 new infections occurring last year. While combination antiretroviral therapy has proven to be successful in reducing HIV related morbidity and mortality, the currently available agents are neither capable of eradicating virus nor of restoring HIV specific immunity to levels that allow for permanent discontinuation of treatment. The ability of current vaccine candidates to induce potent neutralizing antibody responses to block infection has been limited. As such, it is crucial to continue testing and evaluating the responses from vaccine strategies aimed at inducing potent antibody responses.